Just to be sure that we are all getting off on the right foot on this, let me excerpt a few lines from the WP entry on brainstorming. All this is well trod terrain, but just to be sure:
Brainstorming – what we are calling here a thinking exercise — is a group creativity technique by which efforts are made to find a range of insights on a specific problem by gathering a list of ideas spontaneously contributed by its members.

Advertising executive Alex F. Osborn began developing methods for creative problem solving in 1939. He was frustrated by employees’ inability to develop creative ideas individually for ad campaigns. In response, he began hosting group-thinking sessions and discovered a significant improvement in the quality and quantity of ideas produced by employees.

He claimed that two principles contribute to “ideative efficacy,” these being “1. Defer judgment,” and “2. Reach for quantity.” Following these principles were his four general rules of brainstorming, established with intention to reduce social inhibitions among group members, stimulate idea generation, and increase overall creativity of the group.

1. Focus on quantity: This rule is a means of enhancing divergent production, aiming to facilitate problem solving through the maxim quantity breeds quality. The assumption is that the greater the number of ideas generated, the greater the chance of producing a radical and effective solution.

2. Withhold criticism: In brainstorming, criticism of ideas generated should be put ‘on hold’. Instead, participants should focus on extending or adding to ideas, reserving criticism for a later ‘critical stage’ of the process. By suspending judgment, participants will feel free to generate unusual ideas.

3. Welcome unusual ideas: To get a good and long list of ideas, unusual ideas are welcomed. They can be generated by looking from new perspectives and suspending assumptions. These new ways of thinking may provide better solutions.

4. Combine and improve ideas: Good ideas may be combined to form a single better good idea, as suggested by the slogan “1+1=3″. It is believed to stimulate the building of ideas by a process of association.

Osborn notes that brainstorming should address a specific question; he held that sessions addressing multiple questions were inefficient. Further, the problem must require the generation of ideas, rather than judgment.